Yeast and Fermentation
YEAST is a single-celled FUNGUS. The most famous species, SACCHAROMYCES CEREVISIAE, has been domesticated for thousands of years. It eats SUGAR and produces ALCOHOL and CARBON DIOXIDE — a process called FERMENTATION. This simple chemistry powers BREAD (CO2 makes dough rise), BEER and WINE (alcohol), and many other foods. Yeast is one of humanity's oldest and most useful microorganisms.
How fermentation works. Yeast cells absorb sugars (glucose, fructose). When OXYGEN is plenty, they breathe normally and grow. When OXYGEN is LIMITED, they ferment — producing alcohol and CO2. Bread dough: yeast eats flour sugars, releases CO2 (causing dough to rise) and tiny alcohol amounts (which evaporate when baked). Beer: yeast ferments grain sugars into alcohol; CO2 escapes (or is captured for fizz).
You add yeast and water to flour. The dough rises. What's actually happening?
Other yeast uses. WINE: yeast ferments grape sugars. BEER: barley malt sugars. SAKE: rice sugars. KOMBUCHA: yeast and bacteria together. NUTRITIONAL YEAST: a deactivated yeast — popular in vegan cooking for its cheesy flavor and B vitamins. BIOLOGICAL RESEARCH: yeast is a model organism for studying eukaryotic cells. Yeast continues to be one of biology and food science's most useful tools.
Watch It Live
In a bowl, mix 1 cup warm water + 1 packet active dry yeast + 1 tsp sugar. Wait 5-10 minutes. Bubbles and foam appear — that is yeast eating, breathing, and growing. You are watching life happen.
Yeast turns simple sugar into food, drink, and biology research subjects. Tiny single cells, enormous impact on human civilization.
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